Doubt in String's

[santhosh.R gowda]

Dear all
i had attened one interview yesterday there the asked me the question below...

String s="abc";
if(s.equals("abc"))
{
}
if("abc".equals(s))
{
}

what is the difference between both the condition...he has given me one hint that under one condition they will differ

[D. Ogranos]

For this particular example, there is absolutely no difference.

In the general case (assuming you don't know what value String s holds), think about what happens in each case if s == null

[zahid zubair]

D. Ogranos is right. Assume s is null.

if(s.equals("abc")) {
} 

throws NullPointerException

but

if("abc".equals(s)) {
} 

will never throw because you know that Left Hand Side string at the compile time itself that it can not be null. And putting a '.' operator on a non-null object will always let your program go smoothly without exceptions.

Else you would be required to code like this:

if( (s != null) && (s.equals("abc") ) {
} 

which unnecessarily brings in another && condition. Ofcourse, there could be tradeoffs if one could not easily understand why you have used "abc".equals(..) instead of the other approach.